Preparation of multi-grade lubricating oil by severe hydrogenation and urea adduction



United States Patent PREPARATION OF MIJLTI-GRADE LUBRICATING 01L BY SEVERE HYDROGENATION AND UREA ADDUCTION Alfred M. Henke, Springdale, and Allen E. Somers, OHara Township, Allegheny County, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed July 27, 1960, Ser. No. 45,531

4 Claims. (Cl. 208264) This invention relates to the preparation of improved lubricating oils and in particular improved multi-grade lubricating oils.

It is known that lubricating oil stocks may be subjected to treatment with hydrogen in the presence of a hydrogenation catalyst at elevated temperature and pressure in order to obtain a lubricating oil having improved lubricating properties, color, etc. In one modification of these known hydrogenation procedures a multi-grade lubricating oil having a high viscosity index is obtained by treatment under relatively severe hydrogenation conditions. See Beuther et al. United States patent application Serial No. 676,039, filed August 2, 1957 (now Patent No. 2,960,- 458). These multi-grade lubricating oils have exceptional properties. However they are not in all cases entirely satisfactory with regard to pour points unless they are dewaxed. While conventional dewaxing procedures improve the pour points of these materials, further improvement in this regard in many cases is desirable.

This invention has for its object to provide an improved procedure for preparing multi-grade oils of low pour point. Another object is to provide a combination procedure of hydrogenation and Wax removal for preparation of multi-grade oils. Other objects will appear hereinafter.

These and other objects of our invention are accomplished by subjecting a lubricating oil stock to treatment with hydrogen in the presence of a hydrogenation catalyst and under conditions which give rise to the formation of multi-grade lubricating oil components. The product thus formed is solvent dewaxed and thereafter subjected to adduction with urea to separate a non-adducted oil having an improved pour point.

As described in the above noted application, multigrade oils may be produced from residual or heavier distillate lube oil stocks or blends thereof and the procedure of our invention is applicable to all such charge stocks. Also, the reaction conditions and catalysts disclosed in the above noted application may be employed in accordance with our invention to obtain a multi-grade lube oil stock.

In general the charge stock should have a moderately high V.'I. above about 50, a viscosity at 210 F. of between about 60 and 200 S.U.S. and in the case of a residual stock it should be deasphalted. This charge stock is hydrogenated utilizing a pressure above about 2000 p.s.i. and preferably between about 2500 and 4000 psi. A temperature of between about 735 and 825 F. and a space velocity between about 0.4 and 2.5 is employed. The catalyst may be supported or unsupported and is a mixture of a sulfide of the iron group and a sulfide of a metal of group VI left-hand column of the periodic system such as for instance a mixture of nickel and tungsten sulfides. These catalysts promote formation of multi-grade components by aromatic hydrogenation and ring scission. In the event these catalysts are supported they may be deposited on a carrier such as alumina, silica-alumina, pumice, etc. Deposition may be accomplished by impregnating the carrier with aqueous solutions of salts of the metals. The salts are then converted into the oxides which may in turn be sulfided in any known manner to obtain the supported sulfide catalyst. It is advantageous for these carriers to have a cracking index above about 12 as explained in application Serial No. 829,216, filed July 24, 1959, Beuther et al.

The multi-grade lube oil product produced as described above may be subjected to distillation to remove volatile materials formed during the hydrogenation and to obtain the multi-grade lube oil components and these components are then subjected to solvent dewaxing. Alternatively the entire product may be treated with solvent to remove wax in known manner. For instance the well known process of dewaxing by cooling the lube oil stock to be dewaxed in the presence of a mixture of methyl ethyl ketone and toluene may be employed. Ordinarily this cooling is at a temperature of about 0 F. to 10 F. although lower or somewhat higher temperatures may be employed. While we prefer to employ this particular solvent, any other method of solvent dewaxing such as those involving the use of propane, ethylene dichloride-benzene etc. may be employed.

After solvent dewaxing the hydrogenated lube oil stock may be subjected to distillation or other treatment to remove the solvent employed during the dewaxing. However it is an outstanding advantage of one preferred embodiment of our invention that this step may be advantageously eliminated provided that a solvent which activates the urea adduction, such as a ketone, was employed as the dewaxing solvent. Thus in the case of the use of methyl ethyl ketone-toluene mixtures it is not only unnecessary but advantageous not to remove this solvent after the dewaxing step. The presence of this solvent during subsequent urea adduction has a beneficial eifect on the rate of formation of adduct. However regardless of Whether the solventis or is not removed, the dewaxed lube oil stock is next contacted with urea to form the urea adduct.

The adduction of lubricating oil stocks with urea is known in the art and is described in considerable detail in various articles such as Fetterly, Petroleum Refiner, July 1957, pages -150. All such procedures known in the prior art for urea adduction of lubricating oils may be employed in accordance with our invention. In general the adduction is carried out by slurrying the lubricating oil stock with between about 0.2 and 4.0 parts of granular 0r powdered urea per part of lubricating oil stock. Additives to expedite or accelerate the formation of adducts such as a small amount of water may be employed. Furthermore it is advantageous although not necessary to employ relatively low temperatures such as between about 32 F. and 70 F.

After the adduct is formed the lubricating oil which is not adducted may be separated from the solid adduct by filtration, centrifuging or any other suitable method for separating a liquid from a solid. The adduct. is advantageously washed with a small amount of solvent for the lubricating oil such as benzene in order to remove any unadducted oil adhering to the solid adduct. Thereafter the solid adduct is treated in any well known manner to spring or release the adducted oil. Ordinarily this is accomplished by heating with Water. The adducted oil is then separated from the aqueous solution of urea and dried if necessary.

In the event that the dewaxing solvent has not been removed, it is necessary to remove this solvent before the lubricating oil is in suitable condition for use. Such removal may be accomplished by distillation. Frequently this same distillation will not. only remove the dewaxing solvent, but the wash solvents employed for removing lubricating oil from the interstices of the urea adduct. Therefore this single distillation accomplishes the same purpose as two distillations.

Assuming that the product from the hydrogenation step was fractionated to obtain a multi-grade lubricating oil prior to the solvent dewaxing etc. steps, the above described procedure will result in a finished multi-grade lubricating oil. However, if the entire product or a wide range portion of the hydrogenated product was subjected to the solvent dewaxing etc. operations, these operations yield a mixture of hydrocarbons which must be distilled to obtain one or more multi-grade oils. Therefore in the event such a mixture was used in the dewaxing etc. steps, the product from the foregoing operations is then subjected to fractionation, preferably under vacuum conditions, to obtain a multi-grade oil. This may be a distillation to separate blending components which then may be blended to yield one or more multi-grade oils. Alternatively the distillation may be such as to directly yield a multi-grade oil as a residue or a distillate. In this manner high quality multi-grade oils such as SAE W/20; SAE 10W/30; SAE W/30 or 20W/40 etc. may be prepared which have a pour point of -10 F. or lower. Reference is made to the above mentioned Bent. er et al. Patent 2,960,458 for further details as to the distillation operation.

EXAMPLE I A lubricating oil stock having the inspection shown in Table I was subjected to catalytic hydrogenation under mild, moderate and severe conditions. These conditions are set forth in Table II. The products from these three hydrogenations were topped to 725 F. and then solvent dewaxed with a methyl ethyl ketone-toluene mixture utilizing the same conditions in each dewaxing, i.e. the same amount of solvent and cooling to a temperature of 0 F. After removal of wax and dewaxing solvent these hydrogenated and dewaxed oils had the properties given in Table HI.

The three hydrogenated and dewaxed products were then contacted with 2 parts by weight of urea to 1 part by volume of lubricating oil, 1.3 parts by volume of distilled water, and 0.6 part by volume of methyl ethyl ketone. The slurry was stirred for one hour at room temperature and the non-adducted oil was removed by centrifuging. The slurry was then washed with 1.7 parts of cold (8 C.) benzene while centrifuging at 2000 r.p.m. for 20 minutes. The crystalline phase was then removed from the centrifuge and dissolved in boiling water to release any adducted oil. This led to separation of an oil phase only in connection with the severely hydrotreated oil. (The mild and moderately hydrogenated products were initially treated with 1 part urea to 1 part oil, 0.7 part Water to 1 part oil and 0.3 part methyl ethyl ketone to 1 part oil in an attempt to form an adduct with these lower proportions. However no adduct was formed. Therefore the larger proportions mentioned above were employed but, as indicated, an adduct also was not formed with these larger proportions.)

Table III Condition of run Mild Moderate Severe API 21. 0 25.1 3 1.0

Viscosity. SUV. Sec;

Since no adduct was formed in connection with the lubricating oils produced by the mild and moderate con ditions, the treatment with urea did not alter the pour points or other properties of the hydrogenated oils produced under these conditions. Therefore the data in Table iii are applicable to these oils after attempted urea adduction. The data on the adducted and nonadducted oil derived from the severely hydrotreated oil are given in Table IV together with the mass analyses of the charge, the adducted and non-adducted oils.

Table IV Non-Ad- Charge Adduct ducted Oil Yield. percent by Wt 100 0 4.3 05 7 Viscosity. SUV ec' 100 F. 290 19 300 210 1. 55. 7 50.0 50 3 Viscosity Index 123 13 122 Hydrocarbon Type. percent by Vol.:

Alliance 6. 1 20. 0 5. 2 Noncondensed Cyelonhranes" 71.7 61.2 70.7 Condensed Cycloalkanes. 21. 2 15.0 21. 3 2-R111g 17. S 12. 5 13. 0 3-Ring 2. 9 2. 0 2. 3 l-Rin 0. 5 0. 4 0. n 5-Rrn 0. 1 0. 1 0.3 Benzenes.-. 0. 9 0. 7 2. 7 Naphthalcnes 0.2 0. 1 0. 2

It will be noted from Table IV that the non-adducted oil retains a high V.I. This oil constitutes a high quality multi-grade lubricating oil. Since the V.I. of the adducted oil is very high, it can be employed where minor viscosity changes with temperature above 50 F. are essential.

EXAMPLE II 2.5 wt. urea/1 vol. oil charge 1.3 vol. H O/ 1 vol. oil charge 0.6 vol. MEK/l vol. oil charge Data on the results obtained are given in Table VI.

Table V API: 23.8]

Viscosity, SUV, sec.:

210 F 158 Viscosity index 91 Pour Point, F Iodine No, Gulf 1S 12.2

Sulfur, percent by wt 0.23

These data show that high viscosity index adduct was formed and that removing this adduct lowered the pour point of the charge by F.

We claim:

1. The process which comprises in combination subjecting a deasphalted residual lubricating oil stock to treatment with hydrogen at a temperature between about 735 and 825 F. at a pressure above about 2000 psi at a space velocity between about 0.4 and 2.5 in the presence of a catalyst which promotes aromatic hydrogenation and ring scission, solvent dewaxing to a pour point between about 0 and 10 F., subjecting the hydrogenated and dewaxed oil to aduction with urea and sepa rating non-adducted lubricating oil having a pour point substantially below 0 F.

2. The process which comprises in combination subjecting a deasphalted residual lubricating oil stock to treatment with hydrogen at a temperature between about 735 and 825 F. at a pressure above about 2000 psi. at a space velocity between about 0.4 and 1.5 in the presence of a catalyst which promotes aromatic hydrogenation and ring scission, distilling the hydrogenated oil to separate a multi-grade fraction, solvent dewaxing to a pour point between about 0 and 10 F subjecting the dewaxed oil to adduction with urea, separating an unadducted multi-grade lubricating oil having a pour point substantially below 0 F. and a viscosity index con- 6 siderably greater than the viscosity index of the un-hydrogenated oil.

3. The process which comprises in combination subjecting a deasphalted residual lubricating oil stock to treatment with hydrogen at a temperature between about 735 and 825 F. at a pressure above about 2000 psi. at a space velocity between about 0.4 and 2.5 in the presence of a catalyst which promotes aromatic hydrogenation and ring scission, solvent dewaxing the hydrogenated oil with a ketone-containing solvent to a pour point between about 0 and 10 F., subjecting the dewaxed oil containing the ketone solvent to adduction with urea, separating non-adducted lubricating oil having a pour point substantially below 0 F. and removing the ketone solvent therefrom by distillation.

4. The process which comprises in combination subjecting a deasphalted residual lubricating oil stock to treatment with hydrogen at a temperature between about 735 and 825 F. at a pressure above about 2000 psi. at a space velocity between about 0.4 and 2.5 in the presence of a catalyst which promotes aromatic hydrogenation and ring scission, solvent dewaxing the hydrogenated oil with a mixture of methyl ethyl ketone and toluene to a pour point between about 0' and 10 F., subjecting the dewaxed oil containing the dewaxing solvent to adduction with urea, separating non-adducted lubricating oil having a pour point substantially below 0 F. and removing the dewaxing solvent therefrom by distillation.

References Cited in the file of this patent UNITED STATES PATENTS 2,673,175 Stratford et al. Mar. 23, 1954 2,729,596 Mills Jan. 3, 1956 2,786,015 Axe Mar. 19, 1957 2,861,941 Jancosew et a1 Nov. 25, 1958 2,917,446 Jurado Dec. 15, 1959 2,960,458 Beuther et a1. Nov. 15, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 3 078322 February 19 1963 Alfred M. Henke et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4L line 57 for "O f. read 0 F. column 5 Table VI under the second column heading "Non Adducted Oil line 1 thereof for 9.75" read 97.5 same column line 25 for aduction read adduction Signed and sealed this 8th day of October 1963,

(SEAL) Attest:

EDWIN L. REYNOLDS ERNEST W. SWIDER Attesting Officer Acting Commissioner of Patents 

1. THE PROCESS WHICH COMPRISES IN COMBINATION SUBJECTING A DEASPHALTED RESIDUAL LUBRICATING OIL STOCK TO TREATMENT WITH HYDROGEN AT A TEMPERATURE BETWEEN ABOUT 735* AND 825* F. AT A PRESSURE ABOUT ABOUT 2000 P.S.I. AT A SPACE VELOCITY BETWEEN ABOUT 0.4 AND 2.5 IN THE PRESENCE OF A CATALYST WHICH PROMOTES AROMATIC HYDROGENATION AND RING SCISSION, SOLVENT DEWAXING TO A POUR POINT BETWEEN ABOUT 0* AND 10*F., SUBJECTING THE HYDROGENATED AND DEWAXED OIL TO ADUCTION WITH UREA AND SEPARATING NON-ADDUCTED LUBRICATING OIL HAVING A POUR POINT IN SUBSTANTIALLY BELOW 0*F. 